For 67 years, Vietnam was part of French Indochina. You can still see pockets of French influence from grand old buildings in the cities to the presence of Catholicism, right down to the fluffy baguettes you can find everywhere in Vietnam.
Linguistically, French and Vietnamese are very different. Although French was used for official business and in education during that period, finding people in Vietnam who can speak French today is pretty rare.
But nonetheless some words have been borrowed for foreign items like foods and other such objects that were introduced to Vietnam by the French. These words have of course undergone spelling and pronunciation changes to make them Vietnamese, but the French root is still easily seen.
This Taipei Times article has a more extensive list, but some of those words have definitely fallen out of use in modern Saigon.
Probably the very first, and most significant, French influence on the Vietnamese language was the creation by a French missionary of the Vietnamese roman script (called quốc ngữ) – the writing system which replaced Chinese-style ideograms.