From ErfWiki

Proposed Canon

First Appearance: TBFGK 56

A type of Dwagon.

They, along with pink and yellow, are described as one of the weaker varieties of dwagon.^Erf-b1-p058

Speculation

The purple dwagon breath attack is sonic in nature.^Erf-b1-p079 The speculation is that the attack form is a "breath attack", since it is canon that the purple dwagons have a sonic attack ^{LIAB Text 36}

Real World References

Sonic Drive In is a fast food chain in the south-western United States with some franchises in south-central and south-east.