When you cook meat or fish, you should never reuse raw marinade. With tofu, though, the marinade doesn't have the same health risks. Re-add the marinade to your dish at the end of cooking for more of the recipe's flavour.
Tofu takes on the flavour of whatever you're cooking. Unlike meat or fish, tofu is fine to eat raw, so reusing the marinade is no problem. Serious Eats explains:
A great marinade is a good starting point, and grilling that tofu with the marinade applied to it will only concentrate that marinade's flavour. At the same time, it will also alter it, destroying its more subtle, volatile elements. By saving some of your marinade and reapplying it after the tofu is done cooking, you double up on flavour.
Obviously if your marinade contains anything unsafe to eat raw, don't reuse the marinade. Hit the link for other tofu cooking tips.