<p>In analogy to: <a href="https://3dprinting.stackexchange.com/q/6723/4762">What glues for bonding printed PLA to injection-molded plastic?</a>, what are the best glues to use for PETG?</p>
<p>I mostly print in PETG and have occasional failed prints which I usually reprint. But what if I'd like to repair a print e.g. a split between layers or a part broken off?</p>
<p>Knowing that PETG is more &quot;greasy&quot; than PLA, what typical glues can you use to create a good bond; this question excludes using heat to (re-)bond.</p>

From
forum
Bison plastic - works great for me, only it's not "quick dry" but it's very strong, not brittle, holds PETG and PLA very strongly. 
  Buy paint stripper that is/contains methylene chloride (dichloromethane). It will solvent weld both PLA and PETG.
Or see
other forum
which recommends Eastman-910 (original brand of cyanoacrylate) or any equivalent, polyurethane glue, or even epoxy.