The phrase "filled up" can be replaced with a variety of synonyms to add variety to writing or speech. Some options include: loaded, brimmed, stuffed, stocked, replenished, restocked, topped off, squeezed in, packed, crammed, crowded, piled high, jam-packed, and overflowing. These synonyms can be used in a variety of contexts, such as filling up a gas tank, filling up a glass with water, or filling up a room or container with objects or people. Utilizing synonyms can also add depth and dimension to the tone and style of writing, allowing for a more colorful and descriptive expression.