Of course, a company cannot arbitrarily choose who gets meal vouchers or not. This must be laid down in a collective labor agreement (CLA). The CLA specifies which groups of employees are entitled to meal vouchers.
Meal vouchers also fall under the « equality principle ». This means that as a temp worker, you should always receive the same benefits as a permanent employee doing the same job.
What is a meal voucher?
A meal voucher is a voucher that you can use to buy food. Meal vouchers exist only electronically. They are paid out on a payment card that you can use in the store. Each meal voucher is valid for 12 months.
Again, the amount of a meal voucher depends on the company you work for. That amount is the sum of the employee contribution and the employer contribution. So, you pay a bit yourself, and your employer pays the rest. Usually it is divided this way:
You pay a minimum of €1.09 per meal voucher.
Your employer pays a maximum of €6.91 per meal voucher.
How many meal vouchers will you get?
You get a meal voucher for every day you work. You won't get a meal voucher for days when you were sick, on vacation, or not working for some other reason.
Source:
https://werk.belgie.be/nl/themas/verloning/maaltijdcheques#toc_heading_3