Prepaid meal cards are basically the equivalent of the money paid for the meal. So most of the hotels and restaurants accept them.
Sodexo is one such meal card company that gives such meal cards or tickets. Most of the restaurants show the meal card acceptance banner. If not shown, then you have to go there and explain that to the owner if they accept or not. Most of the METRO cities or the hotels near IT company accept such cards.
Depending on how you got these cards, you can save a lot of money. For example, some companies give out such cards during festival time or celebration within company. Those cards don't attach to your salary. If they are attaching that to your salary then they are deducting it from your earning and you have to claim tax on this separately as gift.
If the salary is not deducted for such tickets or meal cards, then you can save money on the food. And that saved money can be shown in food expenses and tax can be deducted from it.
Anyone can use these tickets or meal cards, there is no eligibility for the same. All you have to do is buy them on your own or get them from employer or the person who is giving that out.
Conditions for such cards is that not all hotels and restaurants accept them. So you're limited with that issues. Also you often are limited to price of specific amount with these cards which is another limitation.