If you can have an “open” flame around and have $20, a portable camping stove work fantastic with an isobutane container (about $3 at Walmart) and last up to two weeks if you don’t go crazy with it. https://www.amazon.com/dp/B00ZA39W6U/ref=cm_sw_em_r_mt_dp_U_AtNzDbXGKNF4Z
Otherwise perhaps a small crock pot in the car or break room when at work to get a night worth of beans, stew, soups ect hot. And it’s easy to just mix in vegetables or whatever you have left to make a hodge podge!
These are what I do when I don’t have access to conventional hot meal methods, it’s kind of a PITA but it beats cold food or being hungry by a mile.
The pocket rocket style stoves rule supreme for boiling water though. My alcohol stove set up does good with a wind screen but not as fast as the $15 amazon propane/butane stove I used. This one I think:
https://www.amazon.com/gp/product/B00ZA39W6U/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
$18 for a two pack. No idea why it's so cheap but I've used it 3 times and worked like a champ.
The Jetboil is nice because it is super efficient, which saves fuel and thus weight over a long trip. The efficiency comes from the pot which has a built in heat exchanger. You can get close to the same performance by getting an Olicamp XTS pot which also has a heat exchanger, but it won't be as efficient as the Jetboil. However it does take practice to be really efficient... for larger groups where you may be cooking real food and heating multiple pots of water, you may end up needing a large canister so fuel efficiency may not be critical.
The MSR Pocket Rocket is ol' reliable, been used by a lot of people over the years. But nowadays it's heavy and bulky, the pot supports don't fold up that much so it won't nest inside any smaller pots. The MSR Pocket Rocket 2 is lighter and more compact so you can fit it inside a pot with the canister, makes it much more convenient to pack.
While MSR is a long trusted brand, there are other stoves out there that are much cheaper and have been very reliable. There's the Etekcity stove which is pretty cheap and reliable. You can buy them individually for a few bucks more, but if you go in with a friend you'll save some cash. Another very popular stove is the BRS-3000T, which is extremely light; however, being so small and light it's not nearly as stable as larger stoves like the MSR PR2. If you just want to heat water in a small Ti pot, it's great, but if you want to try to fry up some eggs and bacon on a frying pan, you'll need to pay attention since it won't hold up the larger pan.
You can buy a cheap Stanley stainless steel pot for $10, it's a little heavy but works fine for boiling water. Amazon just started selling a version of the popular anodized cookset if you only bring the pot it's not that heavy, and the hard anodized surface works pretty well for actual cooking if you want to do that in the future.
edit: fixed link.
I've got this Etekcity stove I'd sell for $20. Never used. https://www.amazon.com/Etekcity-Ultralight-Backpacking-Emergency-Earthquake/dp/B00ZA39W6U
https://www.rei.com/learn/expert-advice/backpacking-stove.html
Here is an article that explains the different backpacking stoves
I'll list some of the cheapest ways to boil water that can then be used for couscous.
Overall your cheapest option will be a homemade alcohol stove. You can google how to make them. But these have some downsides. They can spill, they take a longer time to boil water. Honestly though, they are the lightest and cheapest option, I just don't have any experience with them. r/ultralight loves them. People often burn everclear as their fuel. Then they can drink it also.....
One of the cheapest Isobutane stoves will be an eteckcity burner combined with a toaks titanium pot. Plus the isobutane gas, it should all be around 50$ or 60$
https://www.amazon.com/Etekcity-Ultralight-Backpacking-Emergency-Earthquake/dp/B00ZA39W6U
Or I think Firemaple sells cheap burners too. Even cheaper than Eteck city perhaps. There are so many cheap isobutane burners out there on amazon now a days....
Regardless of which stove you choose, look up how to make a wind screen for the burner.
The MSR pocketrockets are the higher quality, most popular brand name stoves.