The implied information is that the people were told to feast on rich food and sweet drinks. Alternate translation: "eat rich food and drink something sweet" (See: [[rc://en/ta/man/translate/figs-explicit]])
The abstract nouns "joy" and "strength" can be expressed as verbs or adjectives. Alternate translation: "rejoicing in Yahweh will protect you" or "being joyful in Yahweh will be your strong refuge" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])