A tealight only puts out 20-30 W(th) and is pretty dogshit for this purpose. That whole fucking Kraut meme about keeping warm with a tealight and an overturned flower pot is the survival equivalent of "wear a mask." Knockoff portable camp burners (knockoff JetBoils and the like) can be had for $20. Less portable but usable with kitchen hardware camp stoves can be had for $30-40. Slap some propane canisters into your cart and now you're not only better prepared but you're one step closer to camping.